Apparatus for gas analysis



June 6, 1950 B. P. UDALE APPARATUS FOR GAS ANALYSIS Original Filed May 15, 1945 INVENTOR BAA/R /D UDAL E ATTORNEY alcohol, or any other two miscible liquids.

Patented June 6, 1950 Original application May 15, 1945, Serial No. 593,819. Divided and this application April 19, 1946, Serial No. 663,298

1 Claim.

The object of this invention is to measure the i Weight of liquid carried as vapor in a stream of gas, preferably air. The liquid may be water ad y means of an immersion refractometer with an auxiliary prism, I can complete the analysis by getting the percentage of alcohol' and of water in the trapped liquid. This application is a division of my copending application Serial No. 593,819

-led May 15, 1945.

Fig. 1 shows'the preferred form vof my invenf tion.

Fig. 2 is a cross-sectional plan view through the -Dry Ice jacket.

Fig. 3 is a partial side view.

Located at the upper end of a glass tube l is mounted a stopcock II. This entrance tube III is continued down as tube I 2, which passes through an expansion chamber I5. The tube I2 terminates in a small chamber I3. I4 is the outside tube forming the outlet from the upper portion of chamber I 3 and the jacket for the tubeV I 2. Tube yI4 terminatesv in the enlarged chamber I5. I6 is the horizontal gooseneck exit tube leading to thev vertical tube I'I in the upper end of which is 'the stopcock i8 and outlet tube '49. Cloth 28 and rubber support Z'I'protect the chamber I3.

A partition 26 protects the jacket 20 and delays ,the evaporation of the Dry Ice contained in the jacket.

In Fig. 2, 22 and 23 are the half-cylindrical, glass Walls of the jacket. 24 and 25 are the rubber tubes split endways and stretched so that the portion marked 24 lembraces the portion marked V25, and the joint action of these two split rubber tubes 24 and 25 is to hold the glass jacket 22-23 together, so as to retain the Dry Ice in place.

3i is a layer of asbest-os next to the glass 22-23. 32 is a layer of parain outside the asbestos layer 3l. A cloth cone 2l, Fig. 1, is used to cover the top of the Dry Ice container to limit the rate of evaporation of Dry Ice. 29 is. a split, removable y rubber stopper embracing the tube l1.

Operation First, the apparatus is thoroughlyv dried byk drawing dry air through the reilux column to y eliminate the last trace of moisture, a llame is 2 before weighing. Counterweights of the same material are used in the process of weighing to an accuracy of iZ- of l milligram. v11/2 c. c. of Water are delivered into the yabsorber bulb I3 at the end of the reux column I4 by means of a 4microfunnel and a graduated micropipette. The

increase in weight gives the Weight of the water added.

The gas absorber is connected at I0 (by means of a rubber connection '30) tothe supply of vapor to be analyzed through a pipe III. (The microstopcocks were previously lubricated with a mixture of 6B graphite and vacuum grease, which is practically chemically inactive to water or methyl alcohol. The 6B graphite is @applied to the surface of the bore by rubbing from a graphite stick and the vacuum grease is then applied in dabs and warmed gently. The bore is pressed inplace and allowed to cool before rotating.) lPowdered Dry Ice is added to the Dry Ice jacket 20, and for ve minutes is allowed to gradually cool the glass. (Dry Ice, solid CO2 at 56 C. approximately.) Then, a mixture of Dry Ice and methyl yalcolici is added and tapped down with the aid of the flattened end of a thick copper wire. (Temperature equals 72 C.) Acover or Dry Ice is then added,

the top of which is covered WithA a cloth 2|, to cut down evaporation of the Dry Ice. The cooling mixture is 'periodically added to the Dry Ice jacket, until ice hasv formed onY the outside of the rubber outer wall 24, 25 Fig. 2. This indicates that the glass outlet I 'I and the Dry Ice jacket 20 are at their minimum temperature. After this, the jacket will require watching every 15 minutes to 30 minutes, ldepending upon the temper- 'ature and humidity of the laboratory. IIhe inlet Vand outlet stopcocks II and I 3 are then opened and the vapor to beanalyzed is allowed 'to flow through the gas absorber at a measured rate. indicated by a flowmeter in series with the source of the vapor stream and the gas absorber. A stopwatch is used to time the flow so that the exact volume of vapor passing through the gas ab- V'sorber can be calcul-ated. At the termination of the run, the inlet stopcock Il is closed, followed by the closing of the outlet stopcock I8. The Dry Ice jacket 2|) is then removed and the outlet tube I'I wiped free of condensed moistureon the outside. The gas absorber is then disconnected from the gas inletv I 0. The stopcocks Il and I8 are rst opened and then closed to equalizel pressure.

The inletV IQ is freed from any glycerine by wiping with the cleaning solution. The inlet and outlet are swabbed with pipe cleaners to remove any dust particles or cleaning uid. When the gas absorber rises to room temperature, it is then prepared for weighing and weighed to a :0.2 mg. The increase in weight represents the total weight of vapors absorbed by the absorbing liquid, Water in this case, in the given volume of gas passed through the gas absorber.

Analyzing the solution in the bulb of gas Kalosorber:

For the analysis of the percentage composition of methyl alcohol caught in the bulb I 3 of the gas absorber, a reference curve is previously constructed under laboratory conditions.

For the methyl alcohol water system, the immersion prism A (n=1.32539 to 1.36640) and the auxiliary prism No. 3 for use with the immersion prisms A and B of the dipping or immersion refractometer were used. The instrument was checked against a distilled Water blank. Due to the sensitivity of the index of refraction to tem- .perature changes, when using only small quan- .and 30% by weight of methyl alcohol in an aqueous solution. The volume of the absorbing liquid in the gas absorber was chosen so that the resultant percent composition of the solution lay on this portion of the curve (1/2 to 11/2 c. c. of water is used).

After the blank (distilled water) has been run, both stopcocks II and I8 of the gas absorber are opened. The liquid in the bulb I3 is shaken down yinto the expansion chamber I5 (a slight pressure on the inlet I may be necessary), and the stopvcocks II and I8 are then closed.

The liquid is rotated in the expansion chamber I to accomplish mixing and then shaken into ,outlet tube I5 I'I. Then both stopcocks II-IB are carefully opened.

The rst drop of liquid which passes the outlet stopcock I8 is discarded and the second drop is poured onto the horizontal surface of the auxiliary prism, which is immediately transferred to the A prism of the dipping refractometer and screwed into place. The stopeocks I I and I8 of the gas absorber are then closed. The reading of the dipping refractometer is recorded only after a sharp line of demarcation has been obtained and reading remains constant for at least 5 minutes.

v'This indicates equilibrium has been reached.

The prisms are then cleaned with distilled water and a lint-free cloth and a second sample is taken and recorded, making sure that the first drop emerging from the gas absorber is always dislcarded, as it carries with it any contamination in the exit of the Voutlet tube. :referred to the percent methyl alcohol reference curva weight of the solution (water added plus increase "in weight) gives directly the Weight of methyl Ihe reading is 'I'he percentage composition of the total alcohol in the volume of gas passed through the 'gas absorber.

The accuracy between successive samples from the same solution was found to be between $0.03 to i004 scale divisions. "tion'of the reference curve (1.5% to 30% methyl alcohol), a i0.1 scale division gave i0.13% by fweight of methyl alcohol and i0.2 scale division On the straight porgave 0.3% by weight of methyl alcohol.

Gas absorber An accuracy of :r0.2 scale divisions can easily be obtained, counting in all experimental errors, to a 10.1 scale division. Accuracy can be obtained with good control of temperature and other laboratory conditions (such as weighing and care of Dry Ice jacket and handling'of dipping refractometer) The efficiency of the Dry Ice jacket was checked by passing Dry Air at 212 cc./min. through the gas absorber containing 1.8 grams of water. A change in weight of 10.2 mg. to iOA mg. was obtained.

The temperature of Dry Ice is 56 C. and the mixture of Dry Ice and methyl alcohol is 72 C. The freezing point of water is 0 C. and that of a '71.9% by weight of methyl alcohol and Water is 51.3 C. The temperature of the Dry Ice jacket is adequate. Since thf critical temperature of Dry Ice is +31 C., theDry Ice jacket would not be practical at room temperature at or above 31 C. as the Dry Ice would evaporate too fast. A different cooling mixture would have to be used at higher temperatures.-

vGas absorter limitations The gas must contain only two miscible vapors, as any other would act as a contaminant in determining the index of refraction of the resultant solution in the gas absorber. All other water soluble and condensible vapors (-56" C. or 72 C.) must be removed previously.

The flow and pressure of the Vapor stream must be such that the absorbing liquid in the bulb of the gas absorber just reuxes in the vreflux column and is not mechanically splattered too far into the expansion chamber I5. If too great a pressure is used, the liquid might be mechanically forced into the exit tube II-I1, thereby clogging it and allowing vapor vto escape through the exit tube I9.

A slow stream of Vapor gives the best results. It allows time for contact between vapor and absorbing liquid, so that complete absorption of vapors can take place. It allows suicient time of contact of the vapors in the exit tube with the cold temperature (-56" C. to 72 C.) so that condensation of the vapors can take place. (212 cc./min. now of vapors at a pressure of 950 m. m. of mercury and a 1/2 to 11/2 cc. volume of absorbing liquid was used.)

' The stream of air and Vapor descending in tube I 2 reverses in the trap I3 and ascends in tube I4, meeting a descending stream of, cold condensed water and alcohol. An interchange of heat takes place. The air gets colder, the liquid gets warmer. -In the expansion chamber I5, the velocity slows down and the temperature drops and any liquid ,carried up by the air refluxes, that is, it descends.

`This is the principle of a reflux column. The cold jacket 20 surrounding the exit tube I 'I prevents anything except dry aii` escaping to the atmosphere through the outlet I9. .WhatIclaimis:l

Thev method of analysis ofthe vapor contents of a moving stream of gas containing no more than two miscible liquids, one of which is water as vapor comprising the steps; passing the'stream of gas into a liquid vapor trap atV the bottom of a reflux column; drawing the gas through the trap andin heat exchange relationship with the incoming gas ,and at the same time expanding 'thegas; drawing the` expanded gas through a vcooled passage to cause condensation of remaining vapors and consequential reilux action with UNITED STATES PATENTS the incoming gases; Weighing the vapor trap liq- Number Name Date uid after a predetermined oW of gas to determine 1 845 247 Davidson Feb 16 1932 the total vapor content; analyzing the trap liquid 2065114 Cahn et al Dec' 22 1936 for relative percentages of the two miscible 5 2:26-9:569 Williams "Jan' 13: 1942 liquids.

BLAIR PAXTON UDALE. 2,314,201 Elsey Mar. 16, 1943 REFERENCES CITED The following references are of record in the lo file of this patent: 

